In the manufacture of fluorescent lamps mercury is introduced into the lamp envelope through a thin glass tube or tubulation at one end of the lamp. The interior of the lamp is then exhausted through the same tubulation and the tubulation then tipped off or sealed, leaving an extended piece of scrap tubulation which in many instances is contaminated with droplets of mercury. A single fluorescent lamp factory can produce more than 750 pounds of such scrap tubulation each day and the amount of mercury in the scrap, tipped off, tubulations can amount to as much as 24 pounds per day. Scrap glass from a lamp making process is generally returned to the melt in the form of cullet but, of course, glass contaminated with mercury cannot be added to the glass melt but must be discarded. Additionally, care must be taken with respect to the disposal of the mercury contaminated scrap glass since mercury can contaminate the environment. In one prior art operation, part of the mercury is reclaimed from the tubing by centrifuging the contaminated exhaust tubes in water. Aside from giving low recovery rates, this method is expensive, subject to spillage and the possibility exists that through this wet process there can be mercury carry-over into the water which then enters the environment through the sewage system.
Since the tipped off exhaust tubing is the product of a melting process which seals the end of the tubulation still attached to the lamp, it also seals off one end of the scrap tubulation to form a very narrow elongated piece of tubing with only one end open. Attempting to recover the mercury from this tubulation with a wet process has been found to be less than adequate since apparently it is difficult for the liquid to enter the tubulation to perform the cleaning.
It has been found, surprisingly, that a dry process in which very finely divided powder, preferrably either silica or alumina, when added in very small quantities to the scrap glass tubulation and agitated for a very short period of time produces an almost aerosol effect in an enclosed container and quickly and efficiently separates the mercury from the interior of the glass tubulation.